Disk drive with variable track density

ABSTRACT

A method of manufacturing a disk drive is disclosed in which servo information is written in tracks on a disk surface, the track width performance of the associated read/write transducer is measured, the track width performance is analyzed and a data track pitch is established. Based on the data track pitch established, a track location formula for data tracks on the surface is defined. For a disk drive with a plurality of read/write transducer-media surface combinations, a track location formula for data tracks is established for each combination. Disclosed is a method of measuring a track width performance of a read/write transducer which includes the steps of writing a first test pattern having a first waveform with the read/write transducer at location t on the surface of a magnetic medium, reading the first test pattern and measuring an error rate of the signal, followed by moving the read/write transducer in a first direction a predetermined distance from location t and writing a second test pattern comprised of a waveform different than the first waveform, moving the read/write transducer in a second direction to a position distance d from location t and writing a third test pattern comprised of a waveform different to the first test pattern. The first test pattern is read at location t and the error rate of the signal is measured. A disk drive including a disk having a first magnetic surface, a first read/write transducer associated with the first magnetic surface for reading and writing data in tracks in a plurality of zones each zone having a read/write frequency, a first load beam for supporting and positioning the first read/write transducer at a plurality of locations above the surface of the magnetic media as disclosed and the drives produced utilizing the steps of writing servo information in tracks on the surface at a track pitch, followed by measuring a track width performance of the read/write transducer and establishing a track pitch for data tracks as a function of the measured track width performance.

This is a Divisional Application of U.S. patent application Ser. No.09/501,711, filed on Feb. 10, 2000, which is herein incorporated byreference in its entirety and assigned to a common assignee.

FIELD OF THE INVENTION

This invention relates to the storage of information on magnetic media,and more particularly to storage of information on moving magneticmedia.

BACKGROUND

It is desirable in recording information on magnetic media to improveand increase the areal recording density to maximize the storageavailable in a given product based upon the components of that product.Several techniques are currently available such as, for example, thosedescribed in U.S. Pat. No. 5,596,458 issued Jan. 21, 1997 to Bruce D.Emo and Brian D. Wilson entitled “Variable Zone Layout For InformationStorage Disk Drive,” also referred to hereinafter as the '458 patent.This patent is assigned to assignee of the present application and thepatent is incorporated herein by reference in its entirety. In the '458patent, variable zones are established having boundaries which are afunction of the read/write transducer recording performance. Themeasured read/write performance is used to establish zone boundaries andread/write frequencies for use in each zone. The range of read/writefrequencies to be used for each read/write transducer is established bymeasuring the read/write performance of the transducer. In assembly of adisk drive, for example, using the techniques disclosed in the '458patent, drive servo information is written in tracks to define a datatrack pitch based on expected track width characteristics of theread/write transducer selected for use in the drive. A layout of datazones and their respective frequencies is performed.

In addition to considering the read/write performance characteristics ofread/write transducers and the establishment of zone layouts,measurement of the track width recording performance of a read/writetransducer may be utilized to increase the areal recording density. Bypacking more closely together tracks of data by using the advantagesgained from a narrower track width recording head, the areal density maybe increased and thus the recording surface may be customized based onthe measured track width of signals written by a read/write transducer.This is described in copending commonly assigned U.S. patent applicationSer. No. 08/966,591 filed Nov. 10, 1997, also referred to hereinafter asthe '591 application, which is a continuation of U.S. patent applicationSer. No. 08/538,662 filed Nov. 2, 1995, by Bruce D. Emo and Brian D.Wilson entitled “Variable Zone Layout and Track Pitch ParameterConsiderations for Information Storage Disk Drive,” now abandoned. The'591 application is incorporated herein by reference in its entirety. Inthe '591 application, techniques are described for measuring the trackwidth of read/write transducers and for using the results of the trackwidth to establish a track pitch for a media to be used in associationwith the read/write transducer. After the track pitch is establishedservo information is written in tracks using the measured track width toestablish the track pitch to be used. If the device using the abovedescribed techniques includes a plurality of recording surfaces, thetrack pitch for each surface is customized to maximize the arealrecording density. However, in each read/write transducer mediacombination a unique track pitch may be established. Thus, a servo trackwriting operation with unique pitch spacings will be required for eachsurface. In addition to considering the track width recordingperformance in producing the disk drive, the read/write recordingperformance as described above in the '458 patent may also be used inconstructing disk drive to further increase the recording capability ofa disk drive product.

While both of the foregoing techniques are very useful and provideadvantageous products, it is desirable to increase the efficiency inmanufacturing a product when the track width is being considered as aparameter for maximization of the storage to be able to write eachsurface of the magnetic media with a common servo track pitch ratherthan individualizing the surfaces based on the measured track widthperformance.

SUMMARY

In accordance with the present invention, a method of defining locationsof data tracks for surface of a magnetic medium is provided, themagnetic medium having associated therewith a read/write transducer. Inthe method, servo information is written in tracks on a surface of themagnetic medium at a track pitch, the track width performance of theread/write transducer is measured, and a track pitch for data tracks isestablished based on the track width performance measured.

In another embodiment, the track pitch for the data tracks isestablished to be different than the track pitch for the servo tracks.

In one embodiment of the present invention, the track width performanceis measured using an error rate measurement technique.

In accordance with another aspect of the present invention, a disk driveis provided, the disk drive including a disk having a first magneticsurface and a first read/write transducer associated with the firstmagnetic surface for reading and writing data in tracks in a pluralityof zones, each zone having a read/write frequency, the drive including aload beam for supporting and positioning the read/write transducer at aplurality of locations above the first magnetic surface, the disk drivebeing produced using the steps of writing servo information in tracks onthe disk surface at a track pitch; measuring a track width performanceof the read/write transducer; and establishing a track pitch for thedata tracks as a function of the measured track width performance of theread/write transducer.

In accordance with another aspect of the present invention, the diskdrive is produced using the further step of defining a data tracklocation formula as a function of a servo track location. As a furtherstep in manufacturing a disk drive, the track location formula is storedin a memory. A disk drive in accordance with the present invention isproduced using the further steps of measuring a recording densityperformance of the read/write transducer with respect to the firstmagnetic surface, and establishing the radial boundaries and aread/write frequency for each zone as a function of the recordingdensity performance of the first read/write transducer. In a furtheraspect of the present invention, a disk drive is produced using the stepof measuring a distance of travel of the read/write transducer todetermine a number of data tracks available; and the disk drive isproduced using the further step of defining radial boundaries of aplurality of zones as a function of the number of data tracks available.

In yet another aspect of the present invention, a method is provided formanufacturing a disk drive comprising a disk having a first magneticsurface and a first read/write transducer associated with the firstmagnetic surface for reading and writing data in tracks. The methodcomprises the steps of writing servo information in tracks on themagnetic surface at a track pitch; measuring a track width performanceof the read/write transducer; and establishing a track pitch for datatracks as a function of the measured track width performance of theread/write transducer. In a further aspect, the method includes the stepof defining a data track location formula as a function of a servo tracklocation. The method further includes the step of storing the data tracklocation formula in a memory. In another aspect of the invention, themethod of manufacturing a disk drive includes the steps of measuring arecording density performance of the first read/write transducer withrespect to the first magnetic surface and establishing radial boundariesand a read/write frequency for a plurality of zones as a function of therecording density performance of the first read/write transducer. In afurther aspect, the method may include the step of measuring a distanceof travel of the read/write transducer to determine a number of datatracks a plurality of zones, each zone having a read/write frequency,the drive including a load beam for supporting and positioning theread/write transducer at a plurality of locations above the firstmagnetic surface, the disk drive being produced using the steps ofwriting servo information in tracks on the disk surface at a trackpitch; measuring a track width performance of the read/write transducer;and establishing a track pitch for the data tracks as a function of themeasured track width performance of the read/write transducer.

In accordance with another aspect of the present invention, the diskdrive is produced using the further step of defining a data tracklocation formula as a function of a servo track location. As a furtherstep in manufacturing a disk drive, the track location formula is storedin a memory. A disk drive in accordance with the present invention isproduced using the further steps of measuring a recording densityperformance of the read/write transducer with respect to the firstmagnetic surface, and establishing the radial boundaries and aread/write frequency for each zone as a function of the recordingdensity performance of the first read/write transducer. In a furtheraspect of the present invention, a disk drive is produced using the stepof measuring a distance of travel of the read/write transducer todetermine a number of data tracks available; and the disk drive isproduced using the further step of defining radial boundaries of aplurality of zones as a function of the number of data tracks available.

In yet another aspect of the present invention, a method is provided formanufacturing a disk drive comprising a disk having a first magneticsurface and a first read/write transducer associated with the firstmagnetic surface for reading and writing data in tracks. The methodcomprises the steps of writing servo information in tracks on themagnetic surface at a track pitch; measuring a track width performanceof the read/write transducer; and establishing a track pitch for datatracks as a function of the measured track width performance of theread/write transducer. In a further aspect, the method includes the stepof defining a data track location formula as a function of a servo tracklocation. The method further includes the step of storing the data tracklocation formula in a memory. In another aspect of the invention, themethod of manufacturing a disk drive includes the steps of measuring arecording density performance of the first read/write transducer withrespect to the first magnetic surface and establishing radial boundariesand a read/write frequency for a plurality of zones as a function of therecording density performance of the first read/write transducer. In afurther aspect, the method may include the step of measuring a distanceof travel of the read/write transducer to determine a number of datatracks available. Additionally, the method may also include the step ofdefining radial boundaries of a plurality of zones as a function of thenumber of data tracks available.

In yet another aspect of the present invention, a series of disk drivesis provided in which the drives are each assembled from a predeterminedset of components for a head disk assembly and for drive electronics.The head disk assembly includes a disk having a first magnetic surfaceand a first read/write transducer associated with the first magneticsurface. In a first drive of the series the first magnetic surfaceincludes a plurality of data tracks and a plurality of servo tracks andin the first drive of the series the data tracks and servo tracks have afirst servo-to-data track pitch relationship. In a second drive of saidseries the servo-to-data track pitch relationship of the first magneticsurface is different than the first servo-to-data track pitchrelationship of the first drive of the series.

In a further aspect of the present invention, a series of disk drives isprovided as set forth immediately above in which each head disk assemblyof the drives in the series the disk each includes a second magneticsurface, and each head disk assembly also includes a second read/writetransducer associated with the second magnetic surface. In the firstdrive of the series the second magnetic surface includes a plurality ofservo tracks having a track pitch and a plurality of data tracks havinga track pitch different than the servo track pitch thereby defining aservo-to-data track pitch relationship, and the servo-to-data trackpitch relationship for the second magnetic surface is different than theservo-to-data track pitch relationship of the first magnetic surface.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may be better understood, and its numerousobjects, features, and advantages-made apparent to those skilled in theart by referencing the accompanying drawings.

FIG. 1 is a flow chart illustrating steps used in the practice of thepresent invention;

FIG. 2 illustrates a demodulated signal pair with a normal positionsignal and a quadrature position signal read from a servo track;

FIG. 3 is a perspective view of a portion of a magnetic recording disk;

FIG. 4 is a top plan view of a dynamic head loading disk drive; and

FIGS. 5, 6, 7, 8, and 9 each illustrate flow charts illustrating stepsused in practicing the present invention.

The use of the same reference symbols in different drawings indicatessimilar or identical items.

DETAILED DESCRIPTION

The present invention is particularly applicable to the manufacture ofrigid disk drives which include a head disk assembly which is mated witha circuit board to provide drive electronics for the recording andplayback of information stored on a surface of a magnetic disk. A headdisk assembly is generally understood by those skilled in the art tocomprise a disk supported for rotation about an axis, and an actuator tomove a read/write transducer to a plurality of locations above thesurface of the disk. The actuator may be of the rotary type such as thatdescribed in U.S. Pat. No. 5,448,433, issued Sep. 5, 1995 entitled “DiskDrive Information Storage Device With Baseplate And Cover HavingOverlapping Edge Portions To Provide Protection From ElectromagneticInterference” by James H. Morehouse, et al., or a rotary actuator diskdrive such as that disclosed in U.S. patent application Ser. No.07/766,480 filed Sep. 25, 1991 by James H. Morehouse et al. Entitled“Microminiature Hard Disk Drive”, now U.S. Pat. No. 5,379,191. It also;of course, will be appreciated that the invention described herein maybe utilized in conjunction with disk drives of the dynamic head loadingtype, the contact start stop type, as well as disk drives utilizinglinear actuators. The two above-identified Morehouse et al. Patents,which are incorporated herein by reference in their entirety, areexemplary of hard disk assembly structures suitable use in practicingthe present invention.

In addition to the head disk assembly, drive electronics associated withthe head disk assembly are utilized to accomplish the reading andwriting of information from a surface of a disk including a magneticcoating. It will be appreciated by those skilled in the art thatnumerous types of drive electronic circuits may be utilized inpracticing the present invention. An example of a suitable driveelectronics which may be utilized in building a disk drive in accordancewith applicants' invention are described in U.S. Pat. No. 5,321,560 toStephen R. Cowen issued Jun. 14, 1994. This patent is incorporated byreference herein in its entirety.

Turning to FIG. 1, a flow chart is illustrated which includes thepreliminary steps for producing a disk drive in accordance with thepresent invention. More particularly, the flow chart in FIG. 1illustrates the process to be used for establishing the location of datatracks for one read/write transducer-memory surface combination. A diskdrive having a plurality of read/write transducer-media paircombinations will require repeating the steps illustrated in FIG. 1 foreach combination.

As will be fully described below, the results of performing the steps inFIG. 1 provide data to define track location formula for each of thedata tracks on a media surface as a function of servo track informationwritten on the recording medium in the process performed in step 2.Thus, executing a seek command-involves using the track location formuladata stored in memory to determine the data track location as a functionof the servo track which corresponds to the desired data track.

Referring again to FIG. 1, step 2 may be performed, for example, byrecording servo information as described in the Cowen '560 patentreferred to above. In the Cowen patent, the technique for servopositioning involves the recording of a normal frame in the positionsub-field as well as a quadrature frame in the position sub-field. Thisposition information is demodulated by suitable circuits well known tothose skilled in the art to produce a normal position signal and aquadrature position signal which is offset in phase by a difference of90° from the normal position signal.

FIG. 2 illustrates a demodulated signal pair with the normal positionsignal illustrated in the upper portion of FIG. 2 and indicated byreference character 8, and the quadrature position signal indicated inthe lower portion of FIG. 2 and indicated by reference character 9. Forthis illustration and the example which will be explained below, theservo tracks are illustrated by the solid vertical lines and the datatracks, except in the case of data track 1 which coincides with servotrack 1, are illustrated in vertical dashed lines. As will beappreciated by reference to FIG. 2, the data tracks are offset from theservo tracks, again except in the instance of data track 1. Asillustrated in FIG. 2, which is an illustrative example of ahypothetical performance of a read/write transducer with respect to anassociated magnetic surface, the servo information has been recorded ata track pitch which is greater than the track pitch established for theread/write transducer. In practicing the present invention as has beenpointed out above, the servo information is recorded in tracks prior toa measurement process to determine track width performance of theassociated read/write transducer. In this particular example illustratedin FIG. 2, the servo tracks are written at a track pitch which isgreater than the expected usable track pitch for acceptable performancewith read/write transducers to be used in the disk drive. In thisexample, the ratio is 1.2, which results in data track 2 being at servotrack position 2.2. In similar fashion, it will be noted that data track3 is between servo tracks 3 and 4, and its position is servo track 3.4,which results from adding 1.2 to 2.2, the position of data track 2. Asillustrated in FIG. 1, a track location formula for data tracks isdefined based on the read/write transducer-associated media performanceand the track formula data is stored in memory in the disk drive topermit locating the requested data track as function of the servo trackposition.

It has been found desirable to record the servo tracks at a pitchsomewhat greater than or equal to, the expected data track pitch basedon the expected track width of read/write transducers being used toconstruct the disk drive. Alternatively, although as illustrated in FIG.2 the servo track pitch is greater than the resulting data track pitch,it is possible to achieve the advantageous manufacturing efficiencies ofthe present invention by recording the servo tracks at a slightly lesserpitch than the expected data track pitch which would result in the datatracks being more closely spaced than the servo tracks. Following thetrack spacing technique illustrated in FIG. 2, it has been found thatbest results are obtained when the expected minimum head track widthdimension lies above 60% of the servo track spacing.

In FIG. 2, the positions on the normal and quadrature signals adjacentarrows V₁, V₂, V₃, V₄, and V₅ indicate the points on the normal positionsignal 8 and quadrature position signal 9 which are used to establishthe data track locations for data tracks 1, 2, 3, 4, and 5. It will benoted that at the indicated locations the signals exhibit linear slopes.The slope of the track servo position signal is predetermined and can beused by the servo system to control track position if the slope andintercept voltage are known. The slope determines the servo polarity,while the intercept determines the desired track null position. Inpractice, an AGC or other normalization process calibrates the magnitudeof both servo signals such that intercept voltage can be predicted as afunction of track position offset. Additionally, the slope ispredictable from the know pre-written servo position signal pattern, andit is also known which of the two servo signals will be linear at thedata track locations. For example, in the instance of data track 3illustrated in FIG. 2, only the quadrature position signal 9 is linearat the data track 3 location. Thus, that signal is used for positioningto data track 3. In the case of data track 2, both the normal positionsignal 8 and the quadrature position signal 9 are linear at the datatrack 2 location, thus either signal could be utilized for seeking andfollowing data track 2.

Referring to FIG. 2, it will be noted that the normal position signal 8is selected for data track 1 and the intercept voltage V₁ is zero Voltsbecause the data track position is coincident with the centerline of theservo track position. The intercept voltage for the other data trackpositions illustrated in FIG. 2 are a mixture of negative and positivevoltages, which as mentioned above, are selected based on the positionsignal being utilized having a linear slope at the data track locationbeing sought. It will be appreciated from the above that any tracklocation can be synthesized by using one or the other of the normalposition signal 8 and quadrature position signal 9 by selecting theappropriate intercept voltage for the desired data track.

Returning to FIG. 1, after writing servo information in tracks asdescribed above, and indicated in step 2 of the flow chart, the nextaction taken is to measure the track width performance of the read/writetransducer with respect to its associated media surface. The performancemeasurements may be performed in a number of ways, three of which aredescribed below. The goal in establishing a track pitch for data tracksis, of course, to have the track pitch as high as possible, but not sohigh that the read/write recording performance is below an acceptablelevel for the product.

One method of measuring track width performance of a read/writetransducer involves writing a test pattern on the associated magneticmedia surface using the read/write transducer, reading the test patternand measuring an amplitude of the signal, then erasing a portion of thetest pattern, followed by reading the test pattern and comparing theamplitude of the signal with the amplitude of the signal measured beforethe erase step.

Reference is made to FIG. 3 in conjunction with the followingexplanation of a technique usable for step 3 in FIG. 1, measurement ofthe track width performance for a read/write transducer. Referring toFIG. 3, magnetic recording disk 15 is shown in a perspective, partialdiameter view, with inside diameter (ID) indicated at 16 and outsidediameter (OD) indicated at 17. In determining a track width performanceof a single track written by a read/write transducer, a data pattern iswritten at track t, the center line of which is indicated by referencecharacter 18. Although track t may be arbitrarily located at variouspositions on the disk surface, a position near the outer edge of thedata area is preferable. The written test pattern should preferably be aconstant frequency NRZ signal having a constant amplitude. The frequencyof the test pattern is preferably at or near the highest recordingfrequency which is expected to be used in the disk drive. One techniquewhich may be used in testing for track width performance is to utilizeany standard, well-known head gimbal assembly (HGA) tester to positionthe read/write transducer mounted as part of an HGA above the surface ofmagnetic disk 15.

Next, the recorded test pattern is read and the amplitude of the signalmeasured is stored for future use. After measuring and storing theamplitude of a signal read at track t, the read/write transducer ismoved to track t+1, the centerline of which is indicated by 19 which isa distance d from the centerline of track location t. The distance d is,at the outset, established based on the expected minimum track width ofa read/write transducer of the type under test. If the read/writetransducer has an actual written track width greater than the minimumexpected for the device, then in subsequent tests distance d may need tobe increased. With the read/write transducer at track t+1, a DC erasesignal is written. Next, the read/write transducer is moved to track t−1the centerline of which is indicated by reference character 20. As inthe prior step, the distance d is the minimum expected track width forthe read/write transducer under test. At track t−1, a DC erase signal iswritten. It will of course be appreciated that by writing a DC erasesignal at an expected track width distance on opposite sides of track tany portion of the test pattern which extends wider than the expectedtrack width will be erased by the DC erase signals written adjacent tothe track.

The read/write transducer is then returned to the original position overtrack t, the test pattern is read, and the amplitude of the test patternsignal stored for comparison with the amplitude of the test patternsignal measured prior to writing the DC erase signals on opposite sidesof track t.

A comparison is now made between the amplitudes of the signal read fromtrack t based on before and after writing to the DC erase signals. Basedon the ratio of the signal amplitude after the writing of the DC erasesignals to the signal amplitude before, a proportionate ratio is formedto determine the percentage of the signal remaining.

It will, of course, be appreciated that if the head disk assemblyincludes a plurality of read/write transducer-surface pairs, themeasurement will be separately performed for each of those, and steps 4,5 and 6 of FIG. 1 will also, of course, be repeated in the process ofdefining the data track locations for each read/write transducer disksurface combination.

Alternatively, rather than using the process described above formeasuring track width performance of the read/write transducer, aprocess using a test procedure to determine the error rate performanceat various track pitch values may be utilized to establish the preferredpitch for the data tracks. One example of a technique involving errorrate testing is the test referred to by those skilled in the art as the747 test procedure which provides a measure of the ability of a track toreproduce information reliably as a function of the track pitch. It is,of course, desirable to increase the track pitch to maximize the amountof information which may be stored on a surface. However, as the trackpitch is increased, at some point the track-to-track spacing may be soclose that the error rates for the tracks are unacceptably high. The 747test is well known to those skilled in the art and a discussion of thistest and the techniques used to implement it is found in a text entitled“Magnetic Disk Drive Technology” by Kanu G. Ashar, published by IEEEPress. The book is cataloged by the following number ISBN 0-7803-1083-7.The discussion is found in the above-noted book at pages 257-259 which,are incorporated herein by reference.

Another useful method of measuring track width performance of theread/write transducer which has been found useful involves writing afirst test pattern, followed by reading the first test pattern andmeasuring the error rate of the signal. Next, a second and third testpatterns are written on opposite sides of the first test pattern. Theread/write transducer is returned to the track containing the first testpattern and the error rate of the signal is measured. The error rateread after the writing of the second and third test patterns gives anindication of the minimum track width which will be required to providea suitable and acceptable error rate performance for the read/writetransducer keeping in mind the read/write specifications which need tobe achieved/by the disk drive. Performing the above test provides anindication of the minimum track-to-track spacing which will be possibleyet permit an acceptable read/write performance.

Referring again to FIG. 3 as an aid to describing the error rate testingreferred to immediately above, the read/write transducer for theassociated disk surface is positioned at track t and a first testpattern having a first waveform is written at location t on the surfaceof magnetic recording disk 15. This first test pattern would preferablybe a fixed pattern comprised of combinations of some of the higherfrequency transitions. For example, a pattern of 1T, 1T, 2T, 1T and 3T,repeated continuously, where T is equal to the transition time betweenbits from the encoder, is one which is desirable to use. Next, the errorrate of the signal written at track t is measured, which may be done byconventional measurement techniques. Next, the read/write transducer ismoved to track position t+1 and a second test pattern is written, thistest pattern may be for example a continuous low frequency pattern suchas 11T. Following writing of the second test pattern, the read/writetransducer is moved to track position t−1 and a third test pattern iswritten with the read/write transducer, this test pattern may be forexample also a low frequency pattern, different than the second testpattern. The third test pattern may be, for example, a continuous 12Tpattern in the case where second test pattern is an 11T. The waveformsfor the second and third test patterns preferably are different than thewaveform for the first test pattern. Additionally, the waveform of thesecond and third test patterns are not necessarily the same. It isadvantageous to use different test patterns for the second and thirdwaveforms to avoid constructive or destructive interference. Next, theread/write transducer is moved to track t and the error rate of thesignal measured. Although the primary concern is the error rate of thesignal from track t, as an additional step it may be desirable tocompare the error rate to the error rate of the signal measured beforethe second and third test patterns were written. If the error rates areclose together, that could indicate a bad read/write transducer. Thesupported for a rotation about a pivot point indicated at 32. The rotaryactuator includes a coil 33, which in conjunction with flux plateassembly and magnet (indicated at 34) serves to position read/writetransducer 35 above the surface of disk 26. Read/write transducer 35 maybe implemented with, for example, any of the well known types such asmagneto resistive (MR), or inductive. Suitable types of read/writetransducers, and their construction, are described in Chapters 4-6 ofthe above-described book by Karin G. Asher. This material appears onpages 70-162 which are incorporated herein by reference.

The rotary actuator of disk drive 25 utilizes a dynamic head loadingmechanism which includes lift rod 37 which cooperates with cam surface38 of cam assembly 39 to provide dynamic load and unload of read/writetransducer 35. Integrated circuit 42 includes electronic circuitry usedduring operation of disk drive 25. The definitional angles and distancesillustrated in FIG. 4 correspond to those used in the description of theadaptive zone layout described in the '458 patent. Line 40 indicates thedistance between the pivot point 32 of the rotary actuator and thecenter of rotation C26 of disk 26. This distance is indicated on thedrawing by “D_(am)”. Line 41, which extends from pivot point 32 throughthe center of read/write transducer 35, illustrates the distance frompivot point 32 to the gap of the read/write transducer 35 (gap notshown). This distance is indicated in the drawing by “D_(ag)”.

The rotary actuator, as illustrated in FIG. 4, is positioned between theinner radius (not shown since it is beneath clamp 28) of disk 26 andouter edge 36 of disk 26. For purposes of explanation, the rotaryactuator in FIG. 4 is assumed to be positioned at the inner radius (ir)of a zone N the boundary of which is to be calculated. Angle θ_(N), theangle between lines 40 and 41, indicates the angle to track N. Since thedisk drive of FIG. 4 is a dynamic head loading-type disk drive, theusable outer radius or is determined by the location at which lift tab37 begins to raise read/write transducer 35 off of the surface of disk26. Similarly, the usable inner radius (ir) is determined by the innercrash stop (not shown) which is located beneath the top plate of fluxplate assembly 34.

FIGS. 5-9 illustrate in flow chart form advantageous constructiontechniques for disk drives utilizing the variable track width techniquesdescribed above in connection with FIGS. 1-4. In manufacturing a diskdrive using the present invention, the process flow described in FIG. 1is first performed to establish a track location formula for eachread/write transducer-media surface combination. If the disk driveincludes a plurality of read/write transducer-media surfacecombinations, a formula is established separately for each one of thecombinations. After the track location formula is stored in a memory(step 6), the process of manufacturing is continued and may followseveral paths. For example, referring to FIG. 5, in the disk driveassembly process illustrated after the track formula relationship hasbeen established, the manufacturing moves to step 1203 in which thehead/disk assembly is mated with a circuit board. Next, in step 2401 theboundaries of the data recording zones on the magnetic surface areestablished based on nominal expected read/write frequency performanceof the read/write transducers to be utilized in manufacturing the diskdrive. This layout of data zones would follow the technique in which thefrequency performance capabilities of the read/write transducer are notmeasured, but is rather assumed to fall within a range for allread/write transducers being purchased for manufacturing of the diskdrive product. A layout using this assumption is described in connectionwith FIG. 1 of the '458 patent. Next, in step 1208, the read channelfilters are optimized for each of the zones, which is followed by thestep of certifying the drive and sparing defects in step 1209, andfinally a final drive test is performed in step 1210. In themanufacturing process, according to the FIG. 5 flow chart, significantadvantages are available because each magnetic media surface is writtenwith the same servo track pitch. This simplifies the manufacturingprocess since all media surfaces are written with the same servo trackpitch rather than having a separate servo track pitch for each surfacebased on a measured read/write transducer track width performance.

In the above manufacturing flow process as illustrated in FIG. 5, itwill be noted that the read/write frequency performance for theread/write transducers are assumed to be a nominal value and theperformance advantages of measuring the read/write frequencycapabilities of each the heads with its associated media surface is notconsidered. However, as will be appreciated with regard to FIGS. 6, 7, 8and 9, which are described in detail below, a further improvement in theareal recording density of a disk drive may be achieved by combining theprocess illustrated in FIG. 1 of this application with the additionalprocesses, such as, for example, measuring the location of the inner andouter crash stops of the disk drive to obtain a measurement of theamount of recording space on a radial basis which is available; and ameasurement of the recording density capability of the read/writetransducers and adjusting the read/write frequency as appropriate toachieve an improved product.

Now turning to FIG. 6, after the completion of step 6 in FIG. 1, thehead disk assembly is mated with the circuit board with which it will beassociated as illustrated in step 1203. Next, the location of the innercrash stop is measured (step 1204), followed by the measurement of theouter crash stop (step 1205). Next, the density capabilities of each 6),the process of manufacturing is continued and may follow several paths.For example, referring to FIG. 5, in the disk drive assembly processillustrated after the track formula relationship has been established,the manufacturing moves to step 1203 in which the head/disk assembly ismated with a circuit board. Next, in step 2401 the boundaries of thedata recording zones on the magnetic surface are established based onnominal expected read/write frequency performance of the read/writetransducers to be utilized in manufacturing the disk drive. This layoutof data zones would follow the technique in which the frequencyperformance capabilities of the read/write transducer are not measured,but is rather assumed to fall within a range for all read/writetransducers being purchased for manufacturing of the disk drive product.A layout using this assumption is described in connection with FIG. 1 ofthe '458 patent. Next, in step 1208, the read channel filters areoptimized for each of the zones, which is followed by the step ofcertifying the drive and sparing defects in step 1209, and finally afinal drive test is performed in step 1210. In the manufacturingprocess, according to the FIG. 5 flow chart, significant advantages areavailable because each magnetic media surface is written with the sameservo track pitch. This simplifies the manufacturing process since allmedia surfaces are written with the same servo track pitch rather thanhaving a separate servo track pitch for each surface based on a measuredread/write transducer track width performance.

In the above manufacturing flow process as illustrated in FIG. 5, itwill be noted that the read/write frequency performance for theread/write transducers are assumed to be a nominal value and theperformance advantages of measuring the read/write frequencycapabilities of each the heads with its associated media surface is notconsidered. However, as will be appreciated with regard to FIGS. 6, 7, 8and 9, which are described in detail below, a further improvement in theareal recording density of a disk drive may be achieved by combining theprocess illustrated in FIG. 1 of this application with the additionalprocesses, such as, for example, measuring the location of the inner andouter crash stops of the disk drive to obtain a measurement of theamount of recording space on a radial basis which is available; and ameasurement of the recording density capability of the read/writetransducers and adjusting the read/write frequency as appropriate toachieve an improved product.

Now turning to FIG. 6, after the completion of step 6 in FIG. 1, thehead disk assembly is mated with the circuit board with which it will beassociated as illustrated in step 1203. Next, the location of the innercrash stop is measured (step 1204), followed by the measurement of theouter crash stop (step 1205). Next, the density capabilities of each ofthe heads is measured and the read/write frequency is adjusted asappropriate to maximize the recording density. This is illustrated inFIG. 6 as step 1206 which is described in detail in the '458 patent(which has been incorporated herein by reference). After determining thedensity capability of the heads and adjusting the read/write frequency,data zones are laid as indicated in step 1207. The process of laying outdata zones in step 1207 is described in detail in connection with FIG.13A of the '458 patent and will not be here repeated. Reference to the'458 patent provides the necessary information to explain this step.Next, the read channel filters for each of these zones are optimized(step 1208), followed by step certify drive and spare defects (step1209) and the process is completed by performance of a final drive test(step 1210).

In another method of manufacturing a disk drive in accordance with thepresent invention, the track location formula each read/writetransducer-memory surface pair is determined in the fashion described inconnection with FIG. 1, followed by the steps illustrated in FIG. 7.Comparing FIGS. 6 and 7, it will be noted that a number of common stepsare included and those steps are indicated by common reference characternumbers. In the manufacturing of a disk drive as presented in the flowchart, FIGS. 1 and 7 combined, the data zones are laid out using thetechnique described in the '458 patent, and in particular as describedin connection with FIG. 13B. The manufacturing process illustrated inFIG. 7 shares the advantage of the process illustrated in FIG. 6 in thatthe manufacturing is simplified in the first instance by the ability towrite a common servo track spacing for each of the media surface,followed by the establishment of a data track location formula for eachspecific read/write transducer-media surface.

Referring to FIG. 8, the steps illustrated therein in conjunction withthose in FIG. 1 (in which a track location formula is ascertained foreach read/write transducer-memory surface combination) are utilized withcertain steps which are common with those illustrated in, for example,FIG. 6. In the manufacturing process in accordance with the FIG. 8embodiment, the radial amount of area on the disk for writing of tracksis assumed to be a nominal amount and thus, in contrast to FIG. 6 forexample, the location of the inner and outer crash stops are notdetermined. In other respects, however, the manufacturing processillustrated in FIG. 8 follows that described in FIG. 6, and as isindicated by common reference characters in FIGS. 6 and 8 which indicatecommon steps.

Referring to FIG. 9, an alternative method of manufacturing a disk driveusing the present invention is illustrated. In FIG. 9 after the tracklocation formula is ascertained as described in FIG. 1, steps 1203,1204, 1205, 1207 and 1208, 1209 and 1210 are performed to complete themanufacture of a disk drive. In the method illustrated in FIG. 9, theinner and outer crash stop locations are measured in similar fashion tothose steps illustrated in FIGS. 6 and 7. However, following the crashstop location measurements, the data zones are laid out as described inthe '458 patent and illustrated in FIG. 13C in connection with thatexplanation. After defining the layout of the data zones (step 1207) theremaining steps in the process of FIG. 9 are common to those illustratedin FIGS. 5-8, described above.

One of the advantages of the present invention is that a series of diskdrives may be produced using common head disk assemblies and driveelectronics, that is made from a predetermined set of components, witheach drive in the series exhibiting common characteristics, such asstorage capacity, even though some of the components, such as heads ormedia, in the drives do not meet some minimum standards of performance.In producing a series of disk drives using common components, each disksurface can have servo tracks written with a common track pitch,followed by establishing a data track pitch for each read/writetransducer-media surface combination which will provide acceptableread/write performance while maximizing the areal storage density. Usingthis technique, an increased storage capacity of one read/writetransducer-media surface combination can compensate for a lesserperforming read/write transducer-media surface combination to produce adisk drive meeting a predetermined performance standard, such as, forexample, storage capacity. Each read/write transducer-media surfacecombination can have a different servo-to-data track pitch relationship.This variation in servo-to-data track pitch relationship may exist fromdrive-to-drive, as well as for each disk surface-read/write transducercombination within the same disk drive. In addition to considering datatrack spacing, utilizing the recording density capability parameterconsiderations, one head-media combination may perform sufficientlybetter than another to permit obtaining a storage capacity goal bybetter utilizing the recording capacity of a higher performinghead-media combination to overcome the deficiencies of the lowerperforming head-media combination. Since the zone boundary layouts andthe recording frequencies used within the zones are established based onperformance criteria and the ability of the head media combination toperform, there will be differences in the zone boundary patterns fordisks from drive to drive in the series of drives.

Using the optimization techniques which provide customized servo trackpitch to data track pitch relationships for each read/writetransducer-media surface combination, in addition to utilizing theadaptive zone techniques to take advantage of the recording densitycapabilities of the read/write transducers, permits the more efficientutilization of drive components, provides a better yield, and achievesreduced manufacturing costs from a like set of components drives ofequal capacity may be produced although their internal head diskperformances on a corresponding surface to surface basis will vary. Theability to tailor the head-surface performance characteristics asdescribed herein gives a manufacturer great flexibility in producingdisk drives from components which inevitably vary in performance, sincethe ultimate goal is to provide to the user a storage characteristicsestablished for the series, and it is not required that each drive inthe series be internally the same from a head-disk recording zone layoutstandpoint or from the standpoint of data track locations with respectto servo track locations.

1. A series of disk drives, each drive in the series being assembledfrom a predetermined set of components for a head disk assembly and fordrive electronics, said head disk assembly having a disk with a firstmagnetic surface and a first read/write transducer associated with saidfirst magnetic surface, wherein in a first drive of said series saidfirst magnetic surface includes a plurality of servo tracks having atrack pitch and a plurality of data tracks having a track pitchdifferent than the servo track pitch thereby defining a servo-to-datatrack pitch relationship; and wherein in a second drive of said seriessaid first magnetic surface includes a plurality of servo tracks havinga track pitch and a plurality of data tracks having a track pitchdifferent than the servo track pitch thereby defining a servo-to-datatrack pitch relationship and wherein the servo-to-data track pitchrelationship of said first magnetic surface of said second drive isdifferent than the servo-to-data track pitch relationship of said firstmagnetic surface of said first drive of said series.
 2. A series of diskdrives according to claim 1, wherein the servo track pitch of said firstand second drives are equal.
 3. A series of disk drives according toclaim 1, wherein in each head disk assembly of the drives in the seriesthe disk includes a second magnetic surface and the head disk assemblyfurther includes a second read/write transducer associated with saidsecond magnetic surface, and further wherein in said first drive of saidseries said second magnetic surface includes a plurality of servo trackshaving a track pitch and a plurality of data tracks having a track pitchdifferent from the data track pitch thereby defining a servo-=to-datatrack pitch relationship, wherein said servo-to-data track pitchrelationship for said second magnetic surface is different that theservo-to-data track pitch relationship of said first magnetic surface.4. A series of disk drives according to claim 1, wherein the number ofdata tracks on said first magnetic surface of said first drive isdifferent than the number of data tracks on said first magnetic surfaceof said second drive.
 5. A series of disk drives, each drive in theseries being assembled from a predetermined set of components for a headdisk assembly and for drive electronics, said head disk assembly havinga disk with a first magnetic surface and a first read/write transducerassociated with said first magnetic surface, wherein in a first drive ofsaid series said first magnetic surface includes a plurality of servotracks having a track pitch and a plurality of data tracks having atrack pitch different than the servo track pitch thereby defining aservo-to-data track pitch relationship and a plurality of recordingzones, said recording zones having radial boundaries defined accordingto a first boundary pattern; and wherein in a second drive of saidseries said first magnetic surface includes a plurality of servo trackshaving a track pitch and a plurality of data tracks having a track pitchdifferent than the data track pitch thereby defining a servo-to-datatrack pitch relationship and a plurality of recording zones, saidrecording zones having radial boundaries defined according to anotherboundary pattern which is different than said first boundary pattern andwherein said servo-to-data track pitch relationship of said firstmagnetic surface of said first drive is different than saidservo-to-data track pitch relationship of said first magnetic surface ofsaid second drive.
 6. A series of disk drives according to claim 5,wherein in each head disk assembly of the drives in the series the diskincludes a second magnetic surface and the head disk assembly furtherincludes a second read/write transducer associated with said secondsurface, and further wherein in said first drive of said series saidsecond magnetic surface includes a plurality of servo tracks, aplurality of data tracks, and a plurality of recording zones, saidrecording zones having radial boundaries defined according to a secondboundary pattern different than said first boundary pattern.
 7. A seriesof disk drives according to claim 6, wherein said second boundarypattern is different than said another boundary pattern.
 8. A series ofdisk drives according to claim 6, wherein in said second disk drive ofsaid series said second recording surface includes a plurality ofrecording zones having radial boundaries defined according to a thirdboundary pattern, wherein said third boundary pattern is different thansaid another boundary pattern.
 9. A series of disk drives according toclaim 8, wherein said third boundary pattern is different than saidfirst boundary pattern.
 10. A series of disk drives according to claim8, wherein said third boundary pattern is different than said secondboundary pattern.
 11. A series of disk drives according to claim 5,wherein said first and second drives of said series have an equal datastorage capacity, and further wherein the number of data tracks on saidfirst recording surface of said first drive is different than the numberof data tracks on said first recording surface of said second drive. 12.A series of disk drives according to claim 6, wherein said first surfaceof said first drive has a first data storage capacity and said secondsurface of said first drive has a second data storage capacity, andfurther wherein said first data storage capacity is different than saidsecond data storage capacity.
 13. A series of disk drives according toclaim 6, wherein each of said surfaces of said first and second driveshas a data storage capacity, wherein the total data storage capacity ofsaid first drive is equal to the total data storage capacity of saidsecond drive, and further wherein the data storage capacity of onesurface of said first drive is different than the data storage capacityof at least one surface of the second drive.
 14. A disk drive comprisinga disk having a first magnetic surface, a first read/write transducerassociated with said first magnetic surface for reading and writing datain tracks in a plurality of zones, each zone having a read/writefrequency, a first load beam for supporting and positioning said firstread/write transducer at a plurality of locations above said firstsurface, said disk drive produced using the steps of: (a) writing servoinformation on tracks on said surface at a track pitch; (b) measuring atrack width performance of said read/write transducer; and (c)establishing a track pitch for said data tracks as a function of theperformance measured in step (b).
 15. A disk drive according to claim14, wherein said disk drive is produced using the further step of: (d)defining a data track location formula as a function of a servo tracklocation.
 16. A disk drive according to claim 15, wherein said diskdrive is produced using the further step of: (e) storing the data tracklocation formula in a memory.
 17. A disk drive according to claim 14,wherein said disk drive is produced using the further steps of:measuring a recording density performance of the first read/writetransducer with respect to said first magnetic surface; and establishingthe radial boundaries and read/write frequency for each zone as afunction of the recording density capability of the first read/writetransducer.
 18. A disk drive according to claim 14, wherein said diskdrive is produced using the further step of: measuring a distance oftravel of said read/write transducer to determine a number of datatracks available.
 19. A disk drive according to claim 18, wherein saiddisk drive is produced using the further step of: defining radialboundaries of said plurality of zones as a function of the number ofdata tracks available.
 20. A disk drive according to claim 14, whereinsaid disk drive is produced using the further steps of: measuring adistance of travel of said read/write transducer to determine a numberof data tracks available; determining a recording density capability ofthe first read/write transducer with respect to said first magneticsurface; and establishing the radial boundaries and a read/writefrequency for each zone as a function of the number of available tracksand the recording density capability of the first read/write transducer.21. A disk drive according to claim 14, wherein said disk drive isproduced using the further steps of: (d) setting a recording densityperformance of said first read/write transducer; and (e) defining theradial boundaries and read/write frequency for each zone as a Functionof the recording density performance in step (d).
 22. A disk driveaccording to claim 17, wherein said drive is produced by the furtherstep of: (f) comparing the measured recording density capability of thefirst read/write transducer with a target level of performance andadjusting a read/write frequency for the read/write transducer if themeasured performance is below the target performance level.
 23. A diskdrive according to claim 17, wherein the recording density performanceof said first read/write transducer is measured at one radial location.24. A disk drive according to claim 17, wherein the recording densityperformance is measured at a plurality of radial locations.
 25. A diskdrive according to claim 17, wherein the recording density performanceis measured at one read/write frequency.
 26. A disk drive according toclaim 17, wherein the recording density performance is measured at aplurality of read/write frequencies.
 27. A method of measuring a trackwidth performance of a read/write transducer comprising the steps of:(a) writing a first test pattern comprising a first waveform with saidread/write Transducer at a location t on a surface of a magnetic medium;(b) reading said first test pattern and measuring an error rate of thesignal; (c) moving said read/write transducer in a first direction to aposition a distance d from said location t and writing a second testpattern comprised of a waveform different from said first waveform; (d)moving said read/write transducer in a second direction to a position adistance d from said location t and writing a third test patterncomprised of A waveform different from said first waveform; (e) readingsaid first test pattern at said location t, and measuring an error rateof the signal.
 28. The method of claim 27, wherein step (d) said thirdtest pattern is written with a waveform which is the same as thewaveform of said second test pattern.
 29. The method according to claim27, wherein in step (a) an electrical signal is applied to saidread/write transducer to provide a first test pattern with a frequencyin a range of recording frequencies for which the read/write transduceris to be used.
 30. The method according to claim 27, wherein said firsttest pattern has a constant frequency.
 31. The method according to claim27, wherein the distance d is selected to be a minimum width expectedfor a pattern recorded by said read/write transducer.